An intensive effort was directed at studying epidemiologic, virologic, immunologic, and clinical aspects of the acquired immunodeficiency syndrome (AIDS). An ongoing study of over 500 hospital employees has continued to shown a low risk of hospital acquired infection with HIV despite percutaneous or mucosal exposure. Quantitative analysis of isotype specific antibody responses to gag and env gene products of HIV revealed a better prognosis for adult individuals with anti-gag and increased problems for infants of HIV-1 positive mothers who develop IgM anti-env or anti-gag responses. Over 50 per cent of asymptomatic HIV positive individuals were found to have some abnormality of immune function. Over 100 different clinical isolates of HIV have been obtained with no correlation seen between the presence of virus in spinal fluid and clinical neurologic disease. A variety of promonocyte lines were found capable of harboring latent HIV-1 which could be induced with various cytokines. Induction of HIV-1 was associated with induction of IL-1. Peripheral blood CD4 cells infected with HIV-1 were found to be defective in their ability to transcribe IL-2 following stimulation with phorbol ester, but not following stimulation with calcium ionophore. The HIV-induced activation of B cells in vitro was found to be independent of viral infection. Studies utilizing in situ hybridization revealed the presence of HIV RNA in brain, lung, and colonic tissue, usually in association with macrophages. The fine specificity of HIV- specific cytotoxic T cells was examined utilizing lymphoblastoid cell lines infected with recombinant vaccinia viruses expressing different parts of the HIV genome. The HIV specific immune responses of chimps following vaccination with gp160 was studied at the level of T cell blast transformation and neutralizing antibody production. A series of clinical studies were conducted in an attempt to improve the clinical status of patients with AIDS. AZT and alpha interferon were found to have clinical and anti-viral effects in patients with early immunodeficiency. Trials of muramyl tripeptide, bone marrow transplantation with AZT and AZT with alpha interferon are in progress.